able to withstand the shear forces pro-
duced.
- Walls must be stable against bending
and shear forces. Masonry work must have
fully filled joints and strong mortar.
- Load-bearing masonry walls should have
minimum thicknesses of 30 cm; their heights
should not exceed eight times their thick-
nesses (15. 6).
- Masonry walls should be stiffened with
piers at a minimum every 4 m (with mini-
mum sections of 30 x 30 cm), or with posts
that are structurally fixed in the foundation
(i.e. able to take movement) (15. 7).
- Wall corners, joints between walls and
across walls, as well as door openings have
to be stiffened by vertical posts of either
timber or reinforced concrete, which are
structurally fixed in the foundation, or by
buttresses, so that horizontal forces do not
open these elements (15.8, 15.22).
- Walls have to be finished on top by a
ring beam, which has to be adequately
fixed to the walls.
- Extra lintels above doors and windows
should be avoided, and should be formed
by ring beams (15. 21).
- Roofs should be as light as possible.
- The horizontal thrusts of vaults and
domes should be sufficiently contained by
ring beams, buttresses or ties.
- Openings destabilise walls and should
be carefully proportioned (15.23).
There are two basic approaches to design-
ing for earthquake resistance. The first and
most commonly used method is to con-
struct walls, roofs and their joints stiffly
137 Earthquake-resistant building
sandy or silty soils. Light houses, however,
perform better on hard rock than on soft
soil.
- The different parts of a house should not
have foundations on different levels, nor
have differing heights. If they do, then they
should be structurally separated. Since sec-
tions of different heights display differing
resonant frequencies, they should be
allowed to oscillate independently.
- Plans should be as compact as possible,
and should be symmetrical. Circular plans
give better rigidity than rectangular ones
(see 15. 5).
- Foundations have to act like stiff ring
anchors, and should therefore be reinforced.
- Foundations, walls and roofs should
be well fixed to each other, the joints being
15. 2Wattle-and-daub
house after heavy earth-
quake, Guatemala 1976
15. 3Earthquake-prone
areas (Houben, Guillaud,
1984)
15. 4Location of houses
on a slope
15. 5Ground plans
15. 6Wall propotion
15. 7Adobe walls, stabi-
lised by buttresses
15. 8Stabilisation of walls
15. 9Destabilisation
through horizontal impact
of a vertical wall with a
framed structure stabi-
lised by tensile diagonals
dangerous
dangerous dangerous
safe dangerous safe
15. 7
15. 8
- 4
15. 9
